Air bag apparatus, air bag folding method, and air-bag folding device

ABSTRACT

A pouch-shaped air bag ( 12 ) is spread out in a circle. Then, the portion of the air bag ( 12 ) located outside the inflator ( 16 ) is folded into a wave-like pattern from four directions so that four side portions ( 61 ) are formed along the inflator ( 16 ). Next, each one of the four excess portions ( 62 ), which are continuously formed between each two adjacent side portions ( 61 ) and protrude outward, is placed along the outer face of each side portion ( 61 ). Thus, the air bag ( 12 ) can be easily folded compactly that can be smoothly unfolded.

BACKGROUND ART

The present invention relates to an air bag system wherein a folded airbag is inflated and expanded by means of gas. The invention also relatesto a method of folding such an air bag and an apparatus for folding thesame.

An example of conventional air bag systems is an air bag systemincorporated in the steering wheel of a vehicle. This air bag systemessentially comprises a flat, pouch-shaped air bag, a cover that coverssaid air bag, and an inflator adapted to eject gas. Under normalcircumstances, the air bag is folded compactly and stored in the cover.The air bag system is adapted to cause gas to be ejected from theinflator in order to inflate the air bag when a shock resulting from acollision of the vehicle is detected, so that the pressure of theexpansion of the air bag tears the cover and projects the air bagtowards the front of the driver, where the air bag continues to beunfolded and inflated at the same time to reduce the shock received bythe driver.

An example of air bag systems of this type is disclosed in JapanesePatent Laid-open No. 137591/1995, which calls for folding an air baginto a wave-like pattern along a plurality of annular creases thatcoaxially surround the generally cylindrical inflator, and thencompressing the air bag by pushing it toward the inflator. Thus, the airbag is folded into a given shape that can be stored in the steeringwheel. An air bag system having this configuration is adapted to enablethe air bag to tear the cover rapidly at a low pressure and expandsmoothly.

However, the above structure offered in Japanese Patent Publication No.137591/1995 presents problems in that the configuration of a foldingapparatus used for folding an air bag tends to be complicated; it isdifficult to reduce production costs of the system; and that it is notalways easy to fold an air bag into a compact shape, because irregularwrinkles tend to be formed in radial and other directions when the airbag folded into a wave-like pattern is pushed and compressed.

In order to solve the above problems, the present invention relates toan air bag system which is capable of folding an air bag easily into acompact shape, as well as a method and an apparatus for folding an airbag which are capable of folding an air bag easily into a compact shape,simplifying the structure of a system, speeding up of the foldingprocess, reducing production costs and enabling the air bag to besmoothly inflated.

An air bag system according to the present invention includes aninflator adapted to eject gas and a pouch-shaped air bag adapted to beunfolded and inflated toward an occupant of the seat equipped with theair bag system by the gas injected from said inflator, wherein said airbag includes an occupant's side portion positioned in front of theinflator, three or more side portions which are folded into a wave-likepattern, located outside the occupant's side portion and continuouslyconnected to the same, and three or more excess portions, each of whichis located between each two adjacent side portions and placed along theouter face of either or both the adjacent side portions. As the sideportions at which the air bag is folded into a wave-like pattern aredisposed around the outer face of the inflator according to theinvention, the air bag can be smoothly unfolded and expanded toward theoccupant from the occupant's side portion when gas is injected. Inaddition, by connecting the side portions, which are folded in awave-like pattern, to one another through the excess portions andpositioning these excess portions along the outer faces of the sideportions, the device according to the invention is capable of foldingthe air bag compactly while arranging creases in an orderly fashion andreducing irregular wrinkles which may be formed during the foldingoperation. Furthermore, providing three each or more side portions andexcess portions enables the air bag to be easily folded into a shapewhich is suitable to be housed in a space having a polygonal or circularoutline. In addition, the configuration also makes it possible to injectgas smoothly and rapidly into the excess portions.

By providing each excess portion with a release line portion thatextends continuously from the occupant's side portion to the end of theexcess portion, the invention is capable of separating the folds thatconstitute each side portion from those which constitute the adjacentside portions and smoothly feeding the gas along these release lineportions to the portion surrounding the outer perimeter of the inflator,so that the air bag may be smoothly inflated outward.

As the excess portions can be easily formed by winding them in a uniformdirection around the outer faces of the respective side portions, theinvention simplifies a folding operation.

According to another feature of the invention, an air bag systemincludes an inflator adapted to eject gas and a pouch-shaped air bagadapted to be unfolded and inflated by the gas injected from saidinflator, wherein said air bag includes a bottom portion in which a gasinlet opening is formed, and three or more side portions which arelocated outside the bottom portion, integrally connected to the same andfolded nearly perpendicularly to the bottom portion into a wave-likepattern, the peripheral end of each side portion placed along the outerface of the side portion. With the configuration as above, the air bagcan be folded compactly into a given shape in a substantially orderlyfashion. Furthermore, as three or more side portions are provided, theair bag can be easily folded into a shape which is suitable to be housedin a space having a polygonal or circular outline, and it is alsopossible to inject gas smoothly and rapidly into the entire air bag.

By forming the bottom portion into a generally rectangular shape, theair bag can be easily folded along the edges of the bottom portion in asubstantially orderly fashion into a compact shape.

By providing a release line portion between each two adjacent sideportions in such a manner that each release line portion extendscontinuously from the bottom portion to the outer end of the sideportion, the invention is capable of separating the folds thatconstitute each side portion from those which constitute the adjacentside portions and smoothly feeding the gas along these release lineportions to the portion surrounding the outer cylindrical face of theinflator, so that the air bag may be smoothly inflated outward.

A method of folding an air bag for an air bag system according to theinvention is a method of folding an air bag adapted to be unfolded andinflated by gas flown thereinto, said method calling for folding saidair bag in such a manner as to form three or more side portions, andplacing each excess portion formed between each two adjacent sideportions along the outer face of each side portion. By folding said airbag to form a plurality of side portions and placing each excess portionformed between each two adjacent side portions along the outer face ofeach side portion, the method according to the invention is capable ofeasily folding the air bag neatly into a shape which comprises sideportions and excess portions. Furthermore, by forming three or more sideportions, the air bag can be easily folded into a shape which issuitable to be housed in a space having a polygonal or circular outline,and it is also possible to inject gas smoothly and rapidly into theentire air bag.

By providing a release line portion between each two adjacent sideportions in such a manner that each release line portion extendscontinuously from the portion into which the gas is injected to theouter end of the side portion, the invention is capable of easilyfolding an air bag which is adapted to be smoothly unfolded and inflatedoutward.

According to yet another feature of the invention, the air bag foldingmethod calls for spreading out an air bag flatly, folding the air bag bypushing the same at a plurality of locations, from the peripheral edgetowards the center while limiting the height of the folds of the airbag, and placing the portions that protrude outward along the peripheralface of the folded portion. According to the method described above, asthe height of the air bag is limited, it is possible to fold the air baginto a given shape simply by pushing the spread out air bag toward thecenter and placing the portions protruding outward along the peripheralface of the folded portion. Therefore, the invention is capable ofsimplifying the process of folding an air bag, thereby reducing the timerequired for the process, simplifying the structure of a foldingapparatus used for this process, and reducing costs for the foldingoperation. Furthermore, as the method calls for folding an air bagaround the central portion, it permits the air bag to be smoothly andrapidly unfolded and inflated from the central portion toward theoccupant, when gas flows to the central portion.

An air bag folding apparatus according to the invention includes arelease line forming means to form release line portions in an air bag,each release line portion continuously extending from the portion fromwhich gas flows into the air bag to the edge of the air bag; and afolding means adapted to fold said air bag into a wave-like pattern inthe state where the release line portions are held by the release lineforming means so as to form side portions folded into a wave-likepattern and excess portions extending along the release line portions.According to this configuration, release line portions continuouslyextending from the portion from which gas flows into the air bag to theedge of the air bag are formed by using a release line forming means,and an air bag is folded into a wave-like pattern by using a foldingmeans in the state where the release line portions are held so that sideportions folded into a wave-like pattern and excess portionsrespectively extending along the release line portions are formed.Therefore, by placing the excess portions along the outer faces of theside portions, an air bag which has release line portions and can besmoothly unfolded and inflated outward can be easily folded.

A compressing means for compressing the side portions that are foldedinto a wave-like pattern may be provided so that an air bag can befolded compactly by compressing the side portions with the compressingmeans.

By providing a winding means for placing the excess portions around theperipheral surface of the side portions, a folding operation of an airbag can be made more convenient.

According to yet another feature of the invention, an air bag foldingapparatus includes a loading portion to permit a flatly spread air bagto be placed thereon, a pushing means for pushing the peripheral edge ofthe air bag toward the center, and a height restricting means forrestricting the distance between the air bag and said loading means.With the configuration as above, by pushing a spread out air bag inwardwith a pushing means, the air bag can be folded into a wave-like patternaround the central portion while the height of the air bag is limited bythe height restricting means, the portions which remain unfolded andprotrude outward are wound or otherwise placed around the outer face ofthe folded portion so that the air bag is formed into a given shape.Thus, the invention is capable of simplifying the process of folding anair bag, thereby reducing the time required for the process, simplifyingthe structure of a folding apparatus used for this process, and reducingcosts for the folding operation. Furthermore, as the apparatus isadapted to fold an air bag around the central portion, it permits theair bag to be smoothly and rapidly unfolded and inflated from thecentral portion toward the occupant, when gas flows to the centralportion.

According to yet another feature of the invention, an air bag foldingapparatus includes a plurality of pushing means and a radial positionrestricting means adapted to form lug portions by limiting the movementof the portions of the air bag which are located between each respectiveadjacent pushing means. With the configuration as above, by forming lugportions by using the radial position restricting means when the air bagis pushed toward its center by the pushing means, each one of said lugportions located between each two pushing means and radially protrudingoutward from the central portion, the apparatus is capable of neatlyfolding the portion of the air bag pushed by the pushing means. Theapparatus is also capable of folding the air bag easily into a givenshape by winding or otherwise placing the lug portions around theperipheral surface of the folded portion.

According to yet another feature of the invention, an air bag foldingapparatus includes a winding means for winding the portions whichprotrude outward around the peripheral surface of the folded portion.With the configuration as above, by winding the portion which protrudeout of the folded portion around the peripheral surface of the foldedportion, the apparatus is capable of folding the air bag easily into agiven shape.

According to yet another feature of the invention, an air bag foldingapparatus includes an insertion means adapted to insert a folded air baginto a cover for storing said air bag therein. With the configuration asabove, as there is no need of a special structure for maintaining thefolded shape, the above configuration enables the folding operation tobe completed quickly and simplifies the production of an air bag systemusing an air bag prepared as above.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded perspective view of an air bag system according toan embodiment of the present invention;

FIG. 2 is a sectional view of said air bag system;

FIG. 3 is a perspective view of said air bag system;

FIG. 4 is a schematic illustration to explain the method of folding saidair bag;

FIG. 5 is a top view of the air bag to explain said folding method;

FIG. 6 is a perspective view of the air bag to explain said foldingmethod;

FIG. 7 is a top view of the air bag in the folded state;

FIG. 8 is a perspective view of the air bag in the folded state;

FIG. 9 is a schematic illustration to explain the method of folding anair bag according to a second embodiment of the invention;

FIG. 10 is a top view of a part of an air bag system according to athird embodiment of the present invention;

FIG. 11 is a schematic illustration to explain said air bag foldingmethod according to the third embodiment;

FIG. 12 is a schematic illustration of said air bag system according tothe third embodiment;

FIG. 13 is a top view of an air bag folded according to a fourthembodiment of the invention;

FIG. 14 is a top view of an air bag folded according to a fifthembodiment of the invention;

FIG. 15 is a top view of an air bag folded according to a sixthembodiment of the invention;

FIG. 16 is a top view of an air bag folded according to a seventhembodiment of the invention;

FIG. 17 is a top view of an air bag folded according to an eighthembodiment of the invention;

FIG. 18 is a top view of an air bag folded according to a ninthembodiment of the invention;

FIG. 19 is a perspective view of a part of the air bag to explain themethod of folding said air bag according to the ninth embodiment;

FIG. 20 is a sectional view of said air bag system according to theninth embodiment of the invention viewed from the direction A in FIG. 19to explain the method of folding the same;

FIG. 21 is a schematic illustration of an apparatus used to fold the airbag according to the ninth embodiment of the invention;

FIG. 22 is a schematic illustration to explain the procedure of foldingsaid air bag according to the ninth embodiment of the invention;

FIG. 23 is a schematic illustration to explain the procedure of foldingthe same;

FIG. 24 is a schematic illustration to explain the procedure of foldingthe same;

FIG. 25 is a schematic illustration to explain the procedure of foldingthe same;

FIG. 26 is a schematic illustration to explain the procedure of foldingthe same;

FIG. 27 is a schematic illustration to explain the procedure of foldingthe same;

FIG. 28 is a schematic illustration to explain the procedure of foldingthe same;

FIG. 29 is a schematic illustration to explain the procedure of foldingthe same;

FIG. 30 is a schematic illustration to explain the procedure of foldingthe same;

FIG. 31 is a schematic illustration to explain the procedure of foldingthe same;

FIG. 32 is a schematic illustration to explain the procedure of foldingthe same;

FIG. 33 is a schematic illustration to explain the procedure of foldingthe same;

FIG. 34 is a sectional view of an air bag system according to a tenthembodiment of the invention; and

FIG. 35 is a schematic illustration to explain the procedure of afolding operation of an air bag system according to an eleventhembodiment of the invention.

Further, FIG. 36 is a schematic illustration to explain a method and anapparatus for folding an air bag according to a twelfth embodiment ofthe invention;

FIG. 37 is an exploded perspective view of an air bag system includingsaid air bag;

FIG. 38 is a general view of said folding apparatus;

FIG. 39 is a perspective view of a part of said folding apparatus;

FIG. 40 is a sectional view taken along the line I—I in FIG. 36 toillustrate the operation procedure using said folding apparatus;

FIG. 41 is a sectional view taken along the line I—I in FIG. 36 toillustrate said folding procedure, showing the step subsequent to thatshown in FIG. 40;

FIG. 42 is a sectional view taken along the line II—II in FIG. 36 toillustrate the same;

FIG. 43 is a perspective view of the same, showing the step subsequentto that shown in FIG. 42;

FIG. 44 is a perspective view of the same, showing the step subsequentto that shown in FIG. 43;

FIG. 45 is a perspective view of the same, showing the step subsequentto that shown in FIG. 44;

FIG. 46 is a perspective view of the same, showing the step subsequentto that shown in FIG. 45;

FIG. 47 is a sectional view taken along the line I—I in FIG. 36 toillustrate the same, showing the step subsequent to that shown in FIG.46;

FIG. 48 is a perspective of the same;

FIG. 49 is a perspective view of a pushing means according to anotherembodiment of the invention;

FIG. 50 is a perspective view of a height limiting means according toanother embodiment of the invention;

FIG. 51 is a perspective view of a height limiting means according toyet another embodiment of the invention;

FIG. 52 is a perspective view of a height limiting means according toyet another embodiment of the invention;

FIG. 53 is a top view of a radial position limiting means according toanother embodiment of the invention; and

FIG. 54 is a sectional view of the same taken along the line III—III inFIG. 53.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the configuration of an embodiment of the present invention isexplained hereunder, referring to the attached drawings.

Referring to FIGS. 1 to 3, numeral 1 denotes an air bag system, which ismounted on a boss portion at the center of the body of the steeringwheel of a vehicle so as to protect a passenger of the vehicle (thedriver in case of this embodiment) from the shock of a collision. Thesteering wheel is normally mounted in such a manner as to be capable oftilting within a specified range and normally used at an angledposition. In the explanation hereunder, the side of the air bag system 1that faces the driver or the person seated at the seat equipped with theair bag system is referred to as the upper side or the occupant's side,while the bottom side of the air bag system 1 that faces the body of thevehicle is referred to as the lower side. Further, unless otherwisespecified, the side or the portion of the air bag system 1 facing towardthe upper front part of the vehicle, i. e. the side facing toward thewindshield, is referred to as the front side or the front portion, whilethe side or the portion of the air bag system 1 facing toward the lowerrear part of the vehicle is referred to as the rear side or the rearportion.

The air bag system 1 essentially comprises a base plate 11 made of aflat rectangular metal and adapted to be attached to the body of thesteering wheel, a pouch-shaped air bag 12 to be folded and disposed onthe base plate 11 in the folded state, a cover (a modular cover) 14 tobe attached to the base plate 11 in such a manner as to cover the airbag 12 from above, and an inflator 16 adapted to be attached to the baseplate 11 from underneath the base plate and feed gas into the air bag12.

More precisely, the inflator 16 comprises a generally cylindrical mainbody 16a, which is provided with a flange portion 16 b formed around theouter cylindrical surface of the main body 16 a and a plurality of gasejection holes 16 c for injecting gas, which are formed at specifiedintervals around the outer cylindrical surface of the main body 16 a,above the flange portion 16 b.

The air bag 12 is formed by sewing the perimeters of a pair of fabricmaterials or plies 12 a, 12 b together along their circular outlines sothat the bag is in the shape of a two ply disk when it is spread flat.The air bag has a shape resembling a flattened ball when it is expandedby a gas flow entry thereto. The underside ply of the air bag has acenter portion 21 in which a gas inlet opening 22 in the shape of acircular hole is formed, while the upper side ply defines an occupant'sside portion 23.

The cover 14 is formed as an integral body by means of, for example,injection molding of synthetic resin and comprises a cover portion 26and mounting wall portions 27 extending downward from the back face ofthe cover portion 26. Said cover portion 26 is adapted to cover the bossportion and a part of the four spoke portions. A horn switch mechanism31 is attached to the cover 14. This horn switch mechanism 31 includes amembrane switch 32, a center pad 32 a, an upper ring 34 and a lower ring35, wherein the membrane switch 32, the center pad 32 a and the upperring 34 are adapted to be disposed in a recess 26 a formed in the top ofthe cover portion 26, and the lower ring 35 and disposed at theunderside of the cover portion 26. These members are fastened to thecover portion 26 by means of a plurality of shafts 37, which areinserted from above through these members, and O-rings 38 disposed underthe lower ring 35 and respectively fitted around the shafts 37. Themembrane switch 32 is provided with a sheet-like switch body 33 whosecontact point is closed when it is deformed, and a connector pieceportion 32 b so formed as to extend from the switch body 32 and to bepositioned along the inner surface of a mounting wall portion 27.Further, the center pad 32 a, upper ring 34 and/or the shafts 37 may bedecorated with, for example, an ID mark so as to be used as ornamentalmembers.

In the air bag system 1 described above, the air bag 12 is disposed onthe base plate 11 in such a manner that the gas inlet opening 22 ispositioned to an inflator mounting hole 11 a of the base plate 11 byusing a generally rectangular annular retainer 41 and rivets (not shown)or the like. The inflator 16 is disposed by inserting the main body 16 aupward through the inflator mounting hole 11 a into the gas inletopening 22 so that bolts 41 a projected from the retainer 41 piercethrough the flange portion 16 b. Then, by fitting nuts 43 fromunderneath around the respective bolts 41 a and tightening the nuts inthe above state, the air bag 12 and the inflator 16 are mounted on thebase plate 11 with the air bag 12 and the base plate 11 secured betweenthe retainer 41 and the flange portion 16 b of the inflator 16. In thestate where the air bag 12 folded into a specified shape is covered bythe cover 14, the mounting wall portions 27 of the cover 14 arerespectively fastened to the sides of the base plate 11 with rivets 44.These rivets 44 are fastened to the mounting wall portions 27 that arerespectively provided at the front and rear ends of the cover, withassist plates 45 disposed between the mounting wall portions 27 and therivets 44 and thus engaged with the respective mounting wall portions27. Then, by attaching an inflator cover 46 to the underside of theinflator 16, the assembly of the air bag system 1 is completed.

When a vehicle equipped with an air bag system 1 having the abovestructure receives a shock resulting from a collision of the vehicle orthe like, an igniter of the inflator 16 is actuated by signals from acollision detecting unit (not shown) or the like to cause reaction of apropellant filling the inflator so that gas is instantaneously ejectedthrough the gas ejection holes 16 c formed around the outer wall of theinflator 16 into the air bag 12. As a result, the air bag 12 is rapidlyinflated and unfolded, and the pressure of the expansion tears the cover14 along a tear line which is so formed in the cover as to be weakerthan the remaining part of the cover, thereby forming a breakthroughopening for the air bag 12. In that state, the air bag 12 projects fromthis opening and continues to be unfolded and inflated at the same timein front of the driver so as to protect the driver from the shock of thecollision.

Next, the procedure of folding the air bag 12 is explained referring tothe drawings.

First of all, as shown in FIG. 4, a folding apparatus 51 used for thefolding operation includes an upper folding mold 52 and a lower foldingmold 53 which are adapted to move towards and away from each other. Theupper and lower folding molds 52 and 53 are respectively provided withpistons 54,55. While the lower piston 55 has a lower plug 55 a thatresembles the shape of the inflator 16, the upper piston 54 has an upperplug 54 a to be pressed against the upper surface of the lower plug 55a. Each one of the folding molds 52,53 also has a plurality of foldingplates 56 which may be cylindrical or square tubes or plates so disposedas to coaxially surround the upper plug 54 a or the lower plug 55 a andsupported in such a manner as to be capable of advancing and retreatingindependently of the upper and lower pistons 54,55. As shown in FIG.4(b), the folding plates 56 are so structured that the upper and lowerfolding plates 56 are alternately arranged when the upper and lowerfolding molds 52,53 are close to each other.

As shown in FIG. 4(a), the air bag 12 attached to the base plate 11 isspread into a flat circle and placed on the piston 55 of the lowerfolding mold 53 in the state where there is a sufficient distancebetween the upper and lower folding molds 52,53. In this state, theupper and lower folding molds 52,53 are brought closer to each other sothat the upper and lower folding plates 56 are alternately arranged fromthe innermost plates to the outermost plates. As a result, the spreadair bag 12 is folded into an annular wave-like shape with the gas inletopening 22 at the center, wherein the portion located outside theinflator 16 is folded in the direction perpendicular to the bottomportion 21 in which the gas inlet opening 22 is formed so that thesurfaces of the fabric materials 12 a, 12 b extend vertically along theouter surface of the inflator 16 and bent at the upper and lower ends.In this state, the occupant's side portion 23 formed of the fabricmaterial 12 a is located on the upper surface of the inflator 16.

Next, the upper and lower folding molds 52,53 are moved away from eachother, and, if necessary, the air bag 12 folded in the wave-like shapeis removed from the folding apparatus 51. Then, by means of a jig (notshown) or by hand of an operator, the air bag 12 is pushed inward fromfour directions into a shape shown in FIG. 5, wherein a side portion 61having a generally rectangular outline is formed at each one of the foursides, with the portion between each two adjacent side portions 61serving as an excess portion (a lug) 62 protruding out of the sideportions 61.

Thereafter, as shown in FIG. 6, by means of a jig (not shown) or by handof an operator, each excess portion 62 is flattened so that itshorizontal outline is in a generally rectangular shape having a partwound along the outer face of one of the adjacent side portions 61 andthe remaining part placed along the outer face of the other side portion61. Thus, the air bag 12 is folded in an orderly fashion into aspecified shape such as the one that fits to the shape defined by themounting wall portions 27 of the cover 14. In case of this embodiment,the air bag is folded in a shape having a rectangular plan outline whenviewed from the top as shown in FIG. 7, and as seen as well fromperspective view FIG. 8.

As described above, according to the structure of the presentembodiment, a plurality of side portions 61 that consist of the portionsof the air bag 12 folded into a wave-like pattern are wound around theouter face of the inflator 16 in a shape resembling flower petals sothat only the occupant's side portion 23, which consists of a singlefabric material, i. e. the fabric material 12 a, of the air bag 12 ispositioned on the inflator 16. Therefore, when gas is injected from theinflator 16, the gas is smoothly directed to the inside area of theoccupant's side portion 23, so that the air bag 12 can be smoothlyunfolded and expanded forward from the occupant's side portion 23 at theinitial stage of the expansion. Therefore, the system according to thepresent embodiment is capable of smoothly tearing the tear line of thecover 14 and projecting the air bag 12 without the need of unnecessarilyhigh pressure for injection gas.

By connecting the side portions 61 formed by folding the fabric into awave-like shape by way of the excess portions 62 and placing theseexcess portions 62 along the outer faces of the side portions 61, it ispossible to fold the air bag 12 into a desired compact shape whilepreventing wrinkles from being formed in radial or other irregulardirection and arranging creases in an orderly fashion. Thus, theembodiment is capable of providing a compact air bag system 1, whereinthe air bag 12 can be rapidly and smoothly inflated in the radialdirection after the air bag 12 projects from the cover 14, and alsocapable of increasing the durability of the air bag system.

Especially when folding an air bag 12 into a shape having a rectangularoutline when viewed from the top, it is easy to fold the air bag 12compactly in an orderly fashion along the edges of the rectangularbottom portion 21.

Furthermore, providing three each or more side portions 61 and excessportions 62 enables the air bag to be easily folded into a shape whichis suitable to be housed in a space having a polygonal or circularoutline. In addition, the configuration also makes it possible to injectgas smoothly and rapidly into the excess portions 62.

As a major portion of the air bag 12 is disposed at the sides of theinflator 16 with only the occupant's side portion 23 consisting of asingle fabric material 12 a positioned on the inflator 16, it ispossible to form a space above the occupant's side portion 23 anddispose a horn switch mechanism 31 for blowing the horn in this space.As there is no need of a particularly thin horn mechanism, the inventionaccording to the embodiment is effective in improving reliability of theswitch and reducing the man-hours of an assembly operation. In addition,compared with a structure which calls for supporting an entire air bagsystem in such a manner that the air bag system can be vertically movedvia a horn switch or other similar structures, the embodimentfacilitates mounting of the air bag system on the body of a steeringwheel with increased precision and with an improved appearance.

Although the invention is explained as above referring to the embodimentwhich calls for the folding apparatus 51 including an upper folding mold52 and a lower folding mold 53, each of which is provided with aplurality of cylindrical folding plates 56, the folding plates of theupper and lower folding molds 52,53 may be of various shapes so that theair bag 12 folded into a wave-like pattern may have various outlines.For example, the upper folding mold 52 and the lower folding mold 53 mayeach have four folding plates in the shape of a flat rectangular plateor, in addition to the four flat rectangular plates, four curved foldingplates which also form excess portions 62 at the same time. Furthermore,in the explanation of other embodiments hereunder, the elements similarto those of the first embodiment are identified with same referencenumerals, of which explanation is omitted.

According to the above embodiment, each excess portion 62 is placedalong the outer faces of the two adjacent side portions 61. However, asin a second embodiment shown in FIG. 9, each excess portion 62 is placedalong the outer face of only one of the two adjacent side portions 61.

According to the above embodiment, four side portions 61 are formed sothat the final folded shape of the air bag has a generally rectangularoutline when viewed from the top. However, the air bag may be foldedinto various shapes with a desired number of side portions 61 in orderto match the shape of the air bag with the design or the cover 14 or forany other purposes.

For example, in cases where a pentagonal base plate 71 is used incombination with a steering wheel having three spoke portions as in athird embodiment shown in FIGS. 10 to 12, an air bag 12 is secured bymeans of a retainer 41 that has four corner portions, one each at thefront and rear and at the two lateral ends. After being folded into awave-like shape by means of a jig, the air bag 12 is pushed from thedirection of the outline as shown in FIG. 11(a), so that five each sideportions 61 and excess portions 62 are so formed as to match the shapeof the base plate 71. Then, as shown in FIG. 11(b), both excess portions62 at the front end and the one at the rear end are placed along theouter surface, and the excess portions 62 at both sides are forcedunderneath said three excess portions 62 and placed along the sideportions 61. The two excess portions 62 at the front end are thenarranged in such a manner that one of them overlaps the outer face ofthe other. Thus, the air bag 12 is folded into a generally pentagonalshape as shown in FIG. 11(c) so as to be snugly placed on the base plate71. In this embodiment, the side portions 61 consist of four folds asshown in FIG. 12(a), each fold having a height h1 of 35 mm. Furthermore,as shown in FIG. 12(b), a part of the side portions 61 are positioned onthe top of the inflator 16, and the folds of this portion has a heighth2 of 50 mm.

Other than being simply wound around the side portions 61, each one ofthe excess portions 62 to be placed along the outer faces of the sideportions 61 may be done so in various manners; for example, as in afourth embodiment shown in FIG. 13, each excess portion 62 may be placedalong a side portion 61 with the end of the excess portion folded inwardonce; or, as in a fifth embodiment shown in FIG. 14, with the end of theexcess portion folded outward once; or once outward and then inward asin a sixth embodiment shown in FIG. 15; or, as in a seventh embodimentshown in FIG. 16, the excess portion 62 may be placed along a sideportion 61 by being folded into a wave-like shape with the end thereoffolded outward twice.

Furthermore, when folding an air bag 12 into a shape having arectangular outline when viewed from the top, the four excess portions62 may be bent into waves and placed along the outer faces of the sideportions 61 at both sides as in an eighth embodiment shown in FIG. 17.

When an air bag 12 spread out in a circle is folded according to theconfigurations of the embodiments described above, annular continuouscreases are first formed around the inflator 16, and side portions 61and excess portions 62 are then formed by dividing these annular creaseswith the creases that are perpendicular thereto. However, said creasesare not limited to be annular continuous creases; as in a ninthembodiment shown in FIGS. 18 to 20, each crease may be divided into aplurality of separate portions during or after the folding operation.

Next, the folding procedure according to said ninth embodiment isexplained hereunder referring to the drawings.

First of all, as shown in FIGS. 21 and 22, a folding apparatus 81 usedfor the folding operation includes an upper jig 82, a lower jig 83,pushing jigs 85 serving as a crimping means, and winding jigs 86 servingas a winding means shown in FIG. 33, the upper jig 82 and the lower jig83 vertically arranged, and each pushing jig 85 disposed to a side ofthe lower jig 83. The upper and lower jigs 82 and 83 are respectivelyprovided with pistons 87,88. While the lower piston 88 has a lower plug88 a having a shape resembling the inflator 16, the upper piston 87 hasan upper plug 87 a to be loosely fitted over the lower plug 88 a andpushed against the upper surface thereof. The upper jig 82 also has fourfolding members A1 through A4 which constitute a folding means and soarranged as to cover the upper plug 87 a from above. The lower jig 83 isprovided with four folding members B1 through B4 which constitute afolding means and so arranged as to cover the lower plug 88 a fromunderneath. These folding members A1 through B4 are independently movedup and down by means of a drive unit or drive units such as aircylinders (not shown). As shown in FIG. 22, the folding members A1through B4 respectively include horizontally arranged base plateportions A1 a to B4 a in the shape of a rectangular plate, each baseplate from A1 a to B4 a having folding plates A1 b through B4 b whichvertically extend from the four horizontal ends of the base plate. Thefolding plates A1 b through B4 b are so arranged that the upper foldingplates and the lower folding plates are alternately positioned as shownin FIG. 25 when the folding members A1 through B4 are close to oneanother. Furthermore, as can be understood with reference to FIGS. 22and 27, the folding plates A1 b through B4 b are adapted to support theshape of the folded side portions 61 until excess portions 62 are placedalong the outer faces of the side portions 61.

The lower jig 83 includes an air bag loading portion 91 shown in FIG.24, on which the spread out air bag 12 may be placed. The air bagloading portion 91 is formed over the area excluding, at least, theportion facing the lower folding plates B1 b through B4 b.

The upper jig 82 is provided with four release line forming members 93adapted to be driven in the vertical direction and serve as release lineforming means. Each release line forming member 93 includes a releaseline forming plate 93 a which is disposed between two adjacent foldingplates A1 b through B4 b and stands on one of the lengthwise sides,along a diagonal line of the base plate 11. The release line formingplates 93 a are arranged in such a manner that their lower ends face theupper surface of the air bag loading portion 91, at a minimal distancetherefrom.

The pushing jigs 85 are provided at four locations, i.e. one at eachside, opposite the respective four sets of folding plates A1 b throughB4 b and adapted to be capable of moving toward and away from the lowerplug 88 a that is in a shape resembling the inflator 16 and disposed atthe center of the apparatus. The pushing jigs 85 include pushing plates85 a which stand on a lengthwise side and respectively extend along thefour sides of the base plate 11. As shown in FIG. 27 and other drawings,each pushing plate 85 a is in the shape of an E when viewed from theoccupant's side, with cutout portions formed in order to preventabutment against the corresponding upper folding plates from A1 b to A4b.

As shown in FIG. 33, the winding jigs 86 are respectively positionedalong the lines extended from the four sides of the base plate 11 andadapted to be driven back and forth along these extended lines.

With the configuration as above, the procedure of folding the air bag 12starts with the initial position shown in FIGS. 21 and 22, wherein theupper and lower jigs 82,83 are vertically separated, and the pushingjigs 85 and winding jigs 86 are moved outward, away from one another. Inthis state, the air bag 12 attached to the base plate 11 is spread outin a circle and attached to the lower plug 88 a, with the lower plug 88a inserted into the gas inlet opening 22 of the air bag 12, in otherwords into the inflator mounting hole 11 a of the base plate 11. Then,by means of a pump which is not shown, the air in the air bag 12 isremoved so as to reduce the volume of the air bag 12.

Next, as shown in FIG. 23, the upper plug 87 a of the upper jig 82 islowered so that the occupant's side portion 23 of the upper fabricmaterial 12 a of the air bag 12 is held between the upper plug 87 a andthe lower plug 88 a.

Thereafter, as shown in FIG. 24, the release line forming members 93 arelowered until the lower ends of the release line forming plates 93 aface the upper surface of the air bag loading portion 91, at a minimaldistance therefrom. In this state, the portion of the air bag 12sandwiched between the release line forming plates 93 a and the air bagloading portion 91 is held in a straight line while it is still able tomove slightly.

Then, as shown in FIG. 25, the folding members A1 through B4 are movedcloser to one another until they are alternately arranged. Of the spreadair bag 12, the portion located outside the inflator 16 is foldedperpendicularly to the bottom portion 21 in which the gas inlet opening22 is formed, so that the surfaces of the fabric materials 12 a, 12 bextend vertically along the outer face of the inflator 16 and bent atthe upper and lower ends. Thus, the air bag is folded in the shape ofwaves that surround the gas inlet opening.

At that time, by moving the folding members A1 through B4 from theinnermost member, i. e. in the order of B1, A1, B2, A2, B3, A3, B4 andA4, the folding plates A1 b through B4 b successively come into contactwith the fabric materials 12 a, 12 b. During this process, as the creaseof the first fold which constitutes the side portions 61 and the excessportions 62 is formed while a crease comer point P1 is simultaneouslyformed at the end of each excess portion 62, the air bag 12 spread outin a circle shown in FIG. 26(a) is formed into the shape shown in FIG.26(b), wherein the crease is divided at four points. Then, as shown inFIG. 26(c), the air bag 12 is folded into a wave-like shape along theouter perimeter of the crease of the first fold so that the crease ofthe second fold is formed while a crease corner point P2 is formed atthe end of each excess portion 62. Then, as the air bag 12 is foldedagain in the same manner, the crease of the third fold is formed while acrease corner point P3 is formed at the end of each excess portion 62 asshown in FIG. 26(d). Finally, by folding back the air bag 12 near theouter perimeter, creases p4,p5 are formed. Thus, four each side portions61 and excess portions 62 are formed as shown in FIG. 26(e) and FIG. 27.

When the air bag is in the above state, each excess portion 62 isdivided by a line extending through the crease comer points p1,p2,p3, i.e. a release line portion 75 that extends from the center of the bottomsurface and communicates from the inner portion to the outer edge of theair bag 12. In other words, all the folds that constitute the sideportions 61 and excess portions 62 are separated by said release lineportion 75.

Next, after the release line forming members 93 are elevated orotherwise retreated at need as shown with the arrows in FIG. 27, thepushing jigs 85 are moved upward and then inward as shown in FIG. 28. Asa result, the pushing plates 85 a of the pushing jigs 85 are combinedwith the folding plates A4 b of the outermost folding member A4 andpressed against the outer faces of the respective side portions 61 ofthe air bag 12, thereby holding the shape of the air bag. In this state,the outermost upper and lower folding members A4,B4 are movedrespectively upward and downward to the retreated positions.

Then, the pushing plates 85 a of the pushing jigs 85 are pushed furtherinward until they are combined with the folding plates A3 b of thefolding member A3, and the upper and lower folding members A3,B3 nowlocated at the outermost position, are vertically moved to retreat whilethe pushing plates 85 a are pressed against the air bag 12. While thepushing jigs 85 are advanced by repeating the above steps, the remainingupper and lower folding members A2,B2,A1,B1 and the upper plug 87 a areremoved as shown in FIGS. 29 and 30.

Next, as shown in FIG. 31, the upper folding members A1 through A4 arelowered again, and the pushing jigs 85 are moved backwards outward whilethe shape of the folded air bag 12 is maintained by the folding platesA1 b through A4 b of the folding members A1 through A4 that hold theouter surfaces of the side portions 61 of the air bag.

In this state, the winding jigs 86 are advanced to wind the excessportions 62, which protrude in four directions from the corners,respectively around the adjacent side portions 61 as shown in FIGS. 32and 33 so that the outline of the air bag becomes rectangular whenviewed from the top. Then, by elevating the folding members A1 throughA4 that have been lowered as above and retracting the winding jigs 86,the air bag 12 is folded in an orderly fashion into a specified shapesuch as the one that fits to the shape defined by the mounting wallportions 27 of the cover 14. In case of this embodiment, the air bag isfolded in a shape having a rectangular outline as shown in FIG. 18.

While having the same effects as those of the other embodimentsdescribed above, the ninth embodiment, wherein a release line portion 75that communicates from the inner portion to the outer edge of the airbag 12 is formed, is capable of directing the gas injected into the airbag smoothly to the occupant's side portion 23 of the air bag 12,thereby allowing the air bag 12 to tear the cover 14 and smoothlyproject therefrom. In addition, after the air bag 12 has projected outof the cover 14, the gas injected toward the center of the air bag 12can be smoothly fed toward the outer perimeter so that the air bag maybe smoothly inflated outward.

Although the creases that constitute the side portions 61 and the excessportions 62 are formed successively in the order from the innermostcrease to the outermost crease according to the ninth embodiment, thecreases may be formed simultaneously or in the order according to anyother appropriate criteria by manual operation or by means of a foldingapparatus. Further, a release line portion 75 described above may beapplicable to an air bag 12 according to any other embodiment of theinvention.

Although a space adapted to house a horn switch mechanism 31 is securedabove the inflator 16 according to some of the embodiments including thesecond embodiment, other configurations may also be applicable. Forexample, as in a tenth embodiment shown in FIG. 34, the horizontal sizeof an air bag system 1 may be reduced by using an inflator 102 with asmaller diameter while increasing the height of the air bag system 1 byusing a cover 101 which is not provided with a recess and arranging gasejection holes 101 a in two rows.

In any one of the embodiments described above, a folding operation ofthe air bag 12 may be fully automated by using various foldingapparatuses, or done by fully manual operation or a combination ofmanual operation and a folding apparatus.

Although the embodiments explained as above have a configuration whichis typically shown in FIG. 2, wherein the side portions of the air bagare folded into wave-like folds that consist of precise repetition of aspecified shape by means of jigs disposed above and below the air bag,the invention is not limited to such a configuration; irregularity andunevenness to a certain extent is permissible when folding the air baginto a wave-like pattern. It is assumed that the movement of the air bagduring its inflation can be more easily set by precisely positioningeach crease of the air bag at a specified location. In case of an airbag made of fabric, however, it is difficult to position the creasesprecisely at specified locations in the first place. Also, even if theair bag were folded into somewhat irregular, uneven waves, the movementof the air bag can be controlled sufficiently. In this regard, otherconfigurations such as the one which calls for spreading an air bagflatly and pushing the same inward from the outer perimeter whilelimiting the vertical clearance are also capable of easily folding theair bag compactly and allowing it to smoothly expand forward whilerestricting irregular wrinkles in a radial direction.

Other than mounted on the steering wheel of a vehicle, an air bag system1 according to the invention may be used as an assist air bag systemdisposed in the instrument panel in front of the passenger seat, a sideair bag system disposed at a side of a seat or in a door panel, or arear seat air bag system mounted on the back of a front seat.Furthermore, in addition to a vehicle, the invention is also applicableto any moving body or the like which requires protection from a shock.

For example, as in an eleventh embodiment shown in FIG. 35 which relatesto an air bag system 111 for a passenger seat, an air bag 112 which isso formed as to be in a rectangular shape as viewed from the occupant'sside when it is inflated may be housed in a case 114 having an openingin a rectangular shape as viewed from the occupant's side by followingthe procedure such as pushing the spread air bag 12 inward from theouter perimeter so as to form side portions 115, which are formed byfolding the air bag into a wave-like pattern at four locations, and fourexcess portions 116, each of which protrudes outward in the radialdirection from a corner between two adjacent side portions, and placingthe excess portions 116 along the outer faces of the two longer sideportions 115. Thus, through a simple operation, the air bag 12 can befolded into such a shape as to be contained in a case 114.

Next, a twelfth embodiment of the invention is explained hereunderreferring to FIGS. 36 to 48.

In the same manner as the embodiment shown in FIG. 1, an air bag 201according to the present embodiment as shown in FIG. 37 is adapted to beincorporated in an air bag system 202 to be mounted on the boss portionof the steering wheel of a vehicle. In addition to the air bag 201, thepresent air bag system 202 includes a generally annular retainer 203, abase plate 204 to be attached to the steering wheel, a tearable cover205 which may be made of synthetic resin, and an inflator 206 adapted toeject gas. In the explanation hereunder, the axial direction in whichthe air bag 201 projects, in other words, the side of the person to beprotected by the air bag, is referred to as the upper side (theoccupant's side) and the side facing the body of the vehicle (thesteering shaft) is referred to as the lower side.

The air bag 201 is formed by sewing together nearly identical twocircular fabric materials, i. e. the upper and lower fabric materials,into a flat bag. A gas inlet opening in the shape of a circular hole isformed at the approximate center of the lower fabric material, and boltinsertion holes are formed around the gas inlet opening, one each atfour locations. These fabrics are made of a material having a specifiedstrength, flexibility (superior resilience), air-tightness and heatresistance, such as nylon cloth coated with rubber or the like. Althoughwhat is generally called non-coated nylon (nylon that is not coated) of420 deniers with 53 counts and a thickness of 0.30 mm is used in thepresent embodiment, any other suitable materials, e. g. a fabricproduced by coating a nylon fabric of 420 deniers with 46 counts and athickness of 0.30 mm with silicone rubber.

The retainer 203 is comprised of a generally ring-shaped retainer body203 a and four mounting bolts 203 b extending downward from the retainerbody 203 a. The base plate 204 includes a base plate portion 204 a inthe shape of a generally rectangular flat plate and side plate portions204 b extending from the edges of the base plate portion 204 a as ifformed by bending the edges of the base plate portion 204 a downward. Aninflator mounting hole 204 c is bored through the base plate portion 204a. The cover 205 includes a cover portion 205 a adapted to cover theboss portion and a part of the spoke portion of the steering wheel, anda mounting plate portion 205 b in the shape of a generally square tube.Said cover portion 205 a and the mounting plate portion 205 b are formedas an integral body, and the space defined by these cover portion 205 aand the mounting plate portion 205 b serves as a storage portion tocontain the folded air bag 201. The inflator 206 comprises a generallycylindrical main body 206 a and a flange portion 206 b which is formedaround the outer wall of the main body 206 a, and gas ejection holes 206c for ejecting gas are formed around the outer wall of the main body 206a.

With the configuration as above, the air bag 201 is folded into aspecified shape, which is described later, in the state the retainer 203has been inserted into the air bag beforehand with the mounting bolts203 b protruding outward through the bolt insertion holes. The air bag201 is then inserted into the storage portion of the cover 205 fromunderneath to be stored therein. Thereafter, the base plate 204 isfitted to the storage portion of the cover 205 from underneath, and themounting plate portion 205 b is fastened to the side plate portions 204b by means of reinforcing plates 207 and rivets R. Then, the main body206 a of the inflator 206 is inserted from underneath the base plate 204through the inflator mounting hole 204 c into the gas inlet opening ofthe air bag 201, and, by tightly screwing nuts 208 around the tips ofthe mounting bolts 203 b, the air bag system 202 is assembled, with theportion of the air bag 201 around the gas inlet opening, the base plateportion 204 a of the base plate 204 and the flange portion 206 b of theinflator 206 sandwiched between the retainer 203 and the nuts 208.

In such an event as collision of the vehicle equipped with the air bagsystem, gas is ejected from the inflator 206, thereby unfolding andexpanding the folded air bag 201. The pressure of the expansion tearsthe cover 205 along a tear line formed under specified conditions,thereby forming a breakthrough opening for the air bag 201. In thatstate, the air bag 12 projects from this opening toward the occupant andcontinues to be unfolded and inflated at the same time into a specifiedshape so as to protect the person at the seat equipped with the air bagsystem from the shock of the collision.

Next, a folding apparatus 211 for folding the air bag 201 is explainedreferring to FIGS. 38 and 39. It is to be noted that the entire foldingapparatus 211 is controlled by a control means such as a computer, whichis not shown in the drawings.

The folding apparatus 211 includes a rack 212, to which a horizontallower plate 214 serving as a loading portion and an upper cylinder 215serving as a driving means are fixed. The upper cylinder 215 is locatedabove the center of the lower plate 214 and adapted to be operated byair pressure or the like to support a horizontal upper plate 216, whichserves as a height restricting means, in such a manner that the upperplate 216 is capable of moving up and down.

Four pressure cylinders 218 serving as a driving means are radiallyarranged and fastened to the rack 212 or the lower plate 214. Thesepressure cylinders 218 are adapted to be driven by air pressure or thelike and respectively support pushing members 221 which are adapted tomove toward and away from the center of the lower plate 214 so as toserve as a pushing means (an outer edge pushing means). Each pushingmember 221 is a plate positioned perpendicularly to the horizontal planeof the lower plate 214 and comprises a center portion 221 a and lugforming portions 221 b respectively extending from both ends of thecenter portion 221 a. The center portion 221 a is formed in an arc witha central angle of nearly 45°, which is similar to the outline of theair bag 201 in the completely folded state. Each lug forming portion 221b extends diagonally rearward at an angle of, for example, about 45°with respect to the associated pushing cylinder 218 so that the entirepushing member 221 looks as if spreading rearward.

Lug forming plates 223 serving as a radial position restricting meansare radially arranged in such a manner that each lug forming plate 223is disposed between each two adjacent pushing members 221. Each lugforming plate 223 is in the shape of a generally rectangular plate whichstands on its side like a rib and is connected through a connectingshaft 224 to a lower cylinder 225 as shown in FIG. 42, and adapted to bemoved vertically (or radially) by said connecting shaft 224 so as toproject above and retract below the upper surface of the lower plate214.

An air bag attaching portion 231 that constitutes a winding means isprovided at the center of the lower plate 214. The air bag attachingportion 231 includes a retainer fixing portion 232 and a rotary actuator233 which is joined to the retainer fixing portion 232. The retainerfixing portion 232 includes a folding mold body 232 a in a shape thatresembles the inflator 206 and bolt supporting holes 232 b adapted topermit the mounting bolts 203 b of the retainer 203 to be respectivelyinserted therein. The rotary actuator 233 is adapted to be driven by airpressure or the like to rotate the retainer fixing portion 232 withrespect to the lower plate 214. If it is necessary, a suction portconnected to a suction unit 234 comprised of a vacuum pump or the likemay be formed in the upper surface of the folding mold body 232 a asshown in FIG. 38, etc., so that the air in the air bag 201 may beevacuated.

The air bag attaching portion 231 is connected to and supported by apair of oppositely arranged pushing cylinders 235, which serve as adriving means that constitutes an insertion means. Each pushing cylinder235 has a driving shaft 235 a affixed to the underside of the lowerplate 214 so that the air bag attaching portion 231 may be moved abovethe lower plate 214 by advancing these driving shafts 235 a.

Next, a folding operation (a folding method) using the above foldingapparatus is explained hereunder.

First of all, as shown in FIG. 40, the upper plate 216 is moved upward,and the pushing members 221 and the lug forming plates 223 are thenrespectively retracted outward and downward. In this state, the air bag201 is flatly spread over the lower plate 214 in such a manner that theupper and the lower fabric materials nearly precisely overlap eachother. As an alternative step, the air bag 201 may be flatly spread overthe lower plate 214 in the state where the lug forming plates 223 areadvanced upward. At that time, the retainer 203 is inserted beforehandinto the air bag 201 so that the mounting bolts 203 project downwardthrough the bolt insertion holes. Then, the retainer 203 is fitted inthe retainer fixing portion 232 of the air bag attaching portion 231,and the air bag 201 is positioned by inserting the mounting bolts 203 binto the bolt supporting holes 232 b and inserting the folding mold body232 a into the gas inlet opening.

Thereafter, as shown in FIG. 41, the suction unit 234 may be actuated atneed to suck the air in the air bag 201 so that the upper and the lowerfabric materials are brought into close contact with each other. Then,while the upper plate 216 is advanced downward in order to limit theheight of the air bag 201 when folded, the lug forming plates 223 areadvanced upward to lift the air bag 201 in the manner shown in FIG. 42,where the air bag 201 is supported radially at four locations andslidably pressed against the underside of the upper plate 216. In thatstate, the distance between the upper plate 216 and the lower plate 214ranges from 30 mm to 50 mm, which corresponds to the height of the finalfolded shape of the air bag 201.

Then, as shown in FIG. 36, the pushing members 221 are simultaneouslyadvanced toward the center of the apparatus to push the air bag 201,starting at its outer end toward the final folded shape. The height ofthe air bag 201 is limited by the upper plate 216. In addition, the airbag 201 is made of a fabric having a given resilience. Therefore, thepushed portion is folded into a wave-like pattern wherein creases extendalong the perimeter of the folding mold body 232 a, the creases being inthe shape of coaxially arranged arcs or straight lines. In this state,the portions respectively held by the lug forming plates 223 remainunfolded and form lug portions 236, each of which projects outwardhaving a crease radially extending from the center toward the outerperimeter 201 a. As each lug forming plate 223 and a lug portion 236 aretightly sandwiched between the lug forming portions 221 b of each twoadjacent pushing members 221, the lug portions 236 are ensured to beformed in a specified shape.

Thereafter, as shown in FIG. 43, the pushing members 221 aresimultaneously retracted outward by a short distance to increase thedistance d between the lug forming portions 221 b of each two adjacentpushing members 221, thereby enabling the lug portions 236 to slidealong the lug forming portions 221 b and the lug forming plates 223.Thereafter, the lug forming plates 223 are moved downward.

In this state, the rotary actuator 233 is operated to rotate theretainer fixing portion 232 of the air bag attaching portion 231 in agiven direction at a given speed as shown in FIG. 44, thereby rotatingthe central portion of the air bag 201 contained in the retainer fixingportion 232, so that the lug portions 236 are turned inward until theyare wound around the outer surface of the portion of the air bag whichis folded into a wave-like pattern.

Then, if it is necessary, the pushing members 221 may be simultaneouslyadvanced inward by a short distance to arrange the shape of the air baginto the final folded shape after the lug portions 236 are completelywound inward as shown in FIG. 45,. As an alternative step in case ofneed, the lug forming plates 223 may be returned to the state shown inFIG. 42 and then simultaneously advanced inward by a short distance toarrange the shape of the air bag if it is necessary to form it into thefinal folded shape. In order to enable the air bag 201 to be smoothlyinserted into the cover 205, the process of which is explainedhereunder, the air bag 201 has to be folded into a shape whosehorizontal area is smaller than that of the storage portion of the cover205.

Next, after the upper plate 216 is retracted upward, the cover 205 ispositioned at a given location above the folded air bag 201 as shown inFIG. 46. Then, while the operator holds the cover 205 so as to preventit from moving upward, the pushing cylinders 235 at both sides of thecover are operated to raise the air bag attaching portion 231 to aposition shown in FIGS. 47 and 48, at a given distance from the lowerplate 214, and the completely folded air bag 201 is inserted into thestorage portion of the cover 205. Thus, the process of folding the airbag 201 and installing the folded air bag in the cover 205 is completed.

According to the embodiment of the invention described above, by pushingthe spread out air bag 201 from four directions toward the center bymeans of the pushing members 221 in the state where the height of theair bag 201 is limited by the upper plate 216 that functions as theheight restricting means, the air bag 201 can be folded in such a mannerthat wave-like folds are formed along the four sides of the centralportion of the air bag with the lug portions 236 radially projectingfrom between the folded portions. Then, by placing the lugs 236 alongthe outer face of the folded portions by manual operation or by using anapparatus, the air bag is formed into the final folded shape that can beeasily inserted into the cover 205. According to the process describedabove, a folding operation can be executed through simple movement ofthe cylinder without the need of an apparatus which has a complicatedstructure including members adapted to engage with one another or callsfor a complicated operation in order to fold the air bag 201 into awave-like pattern. Therefore, said process is capable of simplifying thestructure of a folding apparatus 211, reducing its size and productioncosts as well as the time required for the folding operation.Consequently, the process reduces costs for folding an air bag 201 aswell as production costs for an air bag system 202 itself.

As a lug forming plate 223 is provided between each two adjacent pushingmembers 221, lug portions 236 which radially project outward from thecentral portion can be easily and reliably formed when the pushingmembers 221 are advanced to fold the air bag 201.

Further, as an air bag attaching portion 231 for rotating the centralportion of the air bag 201 is provided as a winding means, the air bag201 can be easily folded into the final folded shape by winding the lugportions 236 around the outer surface of the folded portions.

Furthermore, as the process according to the invention allows the foldedair bag 201 to be inserted into the storage portion of the cover 205directly from the folded state, the process does not require a specialstructure for holding the folded air bag in shape and therefore enablesthe folding operation to be completed quickly and simplifies theproduction of an air bag system 202.

According to the process described above, the air bag 201 is foldedalong the perimeter of the central portion where the gas inlet openingis formed. Therefore, when gas is fed from the inflator 206 into thecentral portion, the air bag can be unfolded and inflated smoothly andrapidly from the central portion toward the occupant's side. Thus, theprocess is capable of reducing the pressure of the gas when it tears thecover 205, and unfolding and expanding the air bag 201 smoothly andrapidly with effective use of the gas. In addition, as the process iscapable of reducing the load applied to the attaching portion at whichthe air bag 201 is supported, it enables the simplification of thestructure of the attaching portion.

In the process for folding the air bag 201 shown in FIGS. 36 and 43according to the twelfth embodiment described above, the pushing members221 are advanced once so that the final folded shape may be formed, andthen moved backward in order to enable the winding of the lug portions236. Depending on resilience and other characteristics of the fabric ofthe air bag 201, however, the step shown in FIG. 43 where the pushingmembers 221 are moved backward may be omitted by setting the movingrange of each pushing member 221 closer to the outer end than is shownin FIG. 36 when it advances and enabling the lug portions 236 to slide.

In the process shown in FIGS. 46 to 48, the pushing cylinders 235 aloneserve as the insertion means, and when the folded air bag 201 isinserted into the cover 205, the operator places the cover 205 on agiven location by hand and holds it there. However, either or both theseplacement and holding may be done by using an industrial robot.

According to the above embodiment, an air bag attaching portion 231including a rotary actuator 233 is provided as the winding means.However, the winding means may be comprised of plates adapted to advanceinward and retreat outward so as to push the radially arranged lugportions 236 and wind them around the outer face of the folded portion,or the winding may be done by human hand without providing a particularmeans.

Furthermore, according to the above embodiment, each pushing member 221serving as a pushing means has a structure shown in FIG. 36, wherein thecenter portion 221 a corresponding to a side of the final folded shapeof an air bag is formed in an arc that curves outward when viewed fromthe top, and each lug forming portion 221 b corresponding to a lugforming plate 223 is formed in a straight line when viewed from the top.However, the pushing members 221 may be in various shapes, such as theone shown in FIG. 49 where the center portion 221 a is formed in astraight line when viewed from the top.

Although the upper plate 216 serving as the height restricting means isin such a shape as to cover the entire upper surface of the air bag inthe spread out state as shown in, for example, FIG. 39 according to theembodiment described above, it is not always necessary to cover theentire upper surface of the air bag; for example, the same effect infolding the air bag 201 into a wave-like pattern can be achieved by astructure shown in FIG. 50 where the portions above the respective lugforming plates 223 are removed so that the upper plate 216 covers onlythe areas traveled by the center portions 221 a of the pushing members221 that fold the air bag 201.

Furthermore, the height restricting means is not limited to an upperplate 216, which is a single plate. The same effect in folding the airbag 201 into a wave-like pattern can be achieved by, for example, astructure shown in FIG. 51, where the height restricting means iscomprised of an upper plate 216 and projecting portions 221 d, whereinthe portions of the upper plate 216 respectively located above the areastraveled by the pushing members 221 are cut out, and each projectingportion 221 d is in the shape of a generally rectangular plate thatprojects forward like a flange from the top of the center portion 221 aof each respective pushing member 221. Further, the shape of eachprojection portion 221 d is not limited to the one shown in FIG. 51, butvarious shapes are applicable, such as the one with its end curvedtoward the center in the shape of an arc, and the one shown in FIG. 52,wherein projection portions 221 d are formed on the lug forming portions221 b, at both sides of the center portion 221 a as well as on thecenter portion 221 a. Depending on the shape of each projection portion221 d or resilience of the fabric of the air bag 201, the upper plate216 may be omitted so that the height restricting means is constitutedonly by the projection portions 221 d.

Although the lug forming plates 223 that move back and forth verticallyfrom the lower plate 214 are used as the radial direction restrictingmeans in formation of the lug portions 236 according to the aboveembodiment, the lug forming plates 223 may be provided at the upperplate 216. The lug portions 236 may move back and force vertically fromeither the lower plate 214 or the upper plate 216, or they may moveradially. In yet another configuration, they may be affixed to the lowerplate 214 or the upper plate 216.

It is not always necessary to use a plate-shaped member as the radialposition restricting means, but any structure is applicable as long asit is adapted to maintain the shape of portions of the air bag whichwill not be pushed by the pushing members 221 so that said portions arearranged radially. For example, a clamp device 241 shown in FIGS. 53 and54 may be used instead of the lug forming plates 223. Said clamp device241 essentially comprises radially arranged coil springs 242 and clampbodies 243 respectively attached to the inner ends of the coil springs242, wherein each coil spring is disposed between each two adjacentpushing members 221 with its outer end fastened to the lower plate 214or the like and serves as a biasing means. With the configuration asabove, the lug portions 236 can be formed by advancing the pushingmembers 221 in the state where the vicinity of the outer perimeter 201 aof the air bag 201 are pinched by the clamp bodies 243. According to theabove configuration, the clamp bodies 243 are supported by theirrespective coil springs 242. Therefore, as the diameter of the air bag201 decreases resulting from the motion of the pushing members 221, anappropriate force is applied in the direction of the outer perimeter ofthe air bag, permitting the lug portions 236 of the air bag 201 to beformed neatly without excessive stress.

Depending on the resilience or other characteristics of the air bag 201,each lug portion may be effortlessly formed between each two adjacentpushing members 221, without the need of a radial direction restrictingmeans. Therefore, the radial direction restricting means can be omitted,as the case may be.

According to the embodiment described above, as four lug portions 236are formed, one each at four locations, by means of the respective fourpushing members 221, an air bag can be folded into a shape that fits toa cover 205 having a generally square storage portion when viewed fromthe top. Depending on the shape of the storage portion of the cover orother conditions, however, lug portions may be formed at two, three ormore than five locations. By providing three each or more pushingmembers 221 and lug forming plates 223, in other words by forming lugportions at three or more locations, the air bag can be easily folded insuch a shape as to be smoothly inserted into a generally polygonalstorage portion of the cover 205, which is defined by the mounting plateportion 205 b of the cover 205.

Industrial Applicability

As described above, the present invention relates to an air bag system,a method of folding the air bag to be installed in said air bag system,and a folding apparatus for such an air bag, said air bag system beingadapted to be installed in, for example, the steering wheel, theinstrument panel, a seat or a door panel of a vehicle and protect theoccupant from the shock of a collision.

What is claimed is:
 1. A method of folding an air bag adapted to beunfolded and inflated by gas blown thereinto, comprising the steps of:providing an uninflated air bag of flat outline shape; forming a gasinsertion portion in the air bag; folding the air bag into an annularwave-like shape; pushing the wave-like shaped air bag inwardly from aperipheral edge thereof to form at least three side portions of arectangular outline leaving an excess portion between each two adjacentside portions; and placing at least a part of each excess portion alongan outer face of at least one of the two adjacent side portions of whichit is between.
 2. An air bag folding method as claimed in claim 1, inwhich the folding comprises producing plural folds in the air bag thatconstitute the side portions and each excess portion, the folds beingseparated by a release line portion that extends continuously from thegas insertion portion to an end of each excess portion.
 3. A method offolding an air bag as claimed in claim 1 wherein: said folding comprisespushing said air bag at a plurality of locations, from said peripheraledge towards a center while limiting the height of folds produced in theair bag by said pushing.
 4. A method of folding an air bag as claimed inclaim 1 wherein said folding comprises: pushing at a plurality oflocations offset and at opposing sides from one another.
 5. A method offolding an air bag as claimed in claim 4 in which the folding comprisesproducing plural folds in the bag that constitute the side portions andeach excess portion, the folds being separated by a release line portionthat extends continuously from the gas insertion portion to an end ofthe excess portion.
 6. An air bag folding method as claimed in claim 1,comprising placing another part of each excess portion along an outerface of an other of the two adjacent side portions of which it isbetween.